Communications networks are used to convey a variety of signals such as voice, video, data and the like to subscribers. Service providers are now routing optical fiber deeper into communication networks to increase the bandwidth available to subscribers. Optical fiber to the premises, for example, provides much greater bandwidth than conventional copper cable.
FIG. 1 schematically illustrates two preconnectorized fiber optic cables 10 and 10′ routed to the premises of a subscriber using two different installation techniques. FIG. 1 shows a first preconnectorized fiber optic cable 10 routed to premises 20 in an aerial installation, and a second preconnectorized fiber optic cable 10′ routed to the premises 20 in a buried installation. In the aerial installation, a first end 10a of the preconnectorized cable 10 is attached at a first interface device 12 located at or near a pole 11, and a second end 10b of the preconnectorized cable 10 is attached at a second interface device 14 located at the premises 20. The first interface device 12 may be a closure, a multiport (a device having multiple receptacles), or the like. The second interface device 14 may be a closure, a network interface device (NID), an optical network terminal (ONT), or the like. In the aerial installation, the craft typically uses a pressure clamp 19 such as a p-clamp (shown schematically shown in FIG. 1) to secure the tensioned fiber optic cable 10 at the pole 11 and at the premises 20, which mitigates sag in the cable 10 along the aerial span.
FIG. 2 depicts a 2 PR pressure clamp 19 with a portion of fiber optic cable 10 held therein. The pressure clamp 19 is available from Reliable Power Products of Franklin Park, Ill. The pressure clamp 19 includes a body 19a, a grip 19b, and a wedge 19c that act to clamp the fiber optic cable 10 with increasing frictional force as the tension on the cable increases. The body 19a receives fiber optic cable 10 between the grip 19b and the wedge 19c and squeezes the cable therebetween as tensile forces are applied. The body 19a also has a loop end used for attaching it to structures such as the pole 11 or the premises 20.
The increasing frictional force on the fiber optic cable 10 prevents the fiber optic cable from pulling out of the pressure clamp 19. However, it is possible for the clamping force from the pressure clamp 19 to plastically deform or otherwise damage the fiber optic cable because the grip 19b has dimples and the body 19a has ridges. Conventional fiber optic cables used within pressure clamps may include buffer tubes to protect the fiber from such deformation.
In buried or duct applications, the first and second ends of preconnectorized cable 10′ are respectively connected to an interface device 16 located at a field location 18 such as inside a pedestal, a manhole, a handhole or the like, and a second interface device 14. The interface devices may include a receptacle (not visible) for making the optical connection with a plug end of the preconnectorized fiber optic cable 10′. As in aerial applications, buried or duct applications may also require a rugged fiber optic cable design. For example, the fiber optic cable can encounter rough terrain or rough handling during installation, such as when pulling the cable into a duct. For fiber to the subscriber applications, the preconnectorized fiber optic cable should be robust enough to withstand aerial, buried, and/or duct installations while maintaining suitable optical performance and reliability.
Further, the distance between the pole 11 or the field location 18 to the second interface device 14 varies with each installation, while preselected lengths of preconnectorized fiber optic cable are typically used by the craft. The length of excess slack fiber optic cable length must therefore be stored. Large fiber optic cables may present problems due to the large space required for slack storage. One solution is to carry many different lengths of preconnectorized fiber optic cables into the field, which creates complexity issues for the craft, the service provider, and the manufacturer.